Motor Tracts Flashcards
What muscles does the medial corticospinal tract innervate?
Postural (neck, shoulder, trunk) muscles.
10%
What muscles does the lateral corticospinal tract innervate?
Limb movements (fractionation). 90%
Direct pathway of the corticospinal pathway
Cell bodies arise in cortex.
Axons descend through the posterior limb of the internal capsule.
Continues through the cerebral peduncles, anterior pons, pyramids.
Fibers cross in the pyramids and descends in the lateral column of the SC.
Synapses w/ LMNs in the spinal cord.
Where are areas located in the Homunculus?
Medial is LE.
Middle 1/3 is UE.
Lateral 1/3 is Head/neck.
Where do the UMNs synapse w/ the LMNs in the spinal cord?
Ventral (anterior) horn
Which CNs use the corticobulbar (corticonuclear) tract?
CNs V, VII, IX, X, XI, XII
Corticobulbar tract pathway
The exact same as the corticospinal, EXCEPT: it travels through the genu of the internal capsule, not the posterior limb.
Organization of the ventral (anterior) horn:
Medial LMNs go to axial/postural ms.
Lateral LMNs go to limb ms.
LMNs innervating extensors lie ventral.
LMNs innervating flexors lie dorsal.
Medial LMNs get input from: (5)
Tectospinal tract Medial vestibulospinal tract Medial reticulospinal tract Medial corticospinal tract Lateral vestibulospinal tract
Lateral LMNs get input from: (3)
Rubrospinal tract
Lateral reticospinal tract
Lateral corticospinal tract
Do the cranial nerves in the corticobulbar tract stay ipsilateral, contralateral, or BL?
CN V: BL
CN VII: BL of forehead, CL to low face.
CN IX, X, XI: CL
CN XI: IL
Lateral vestibulospinal tract
Vestibular nuclei to SC.
IL LMNs innervating postural ms. and extensors.
*opposes gravity
Medial vestibulospinal tract
Vestibular nuclei to SC.
To cervical and thoracic levels.
*head movements
Medial (pontine) reticulospinal tract
Pontine RF to SC.
IL LMNs innervating postural ms. and extensors.
*postural reflexes
Lateral (medullary) reticulospinal tract
Medullary RF to SC.
Facilitates flexor motor neurons and inhibits extensor motor neurons.
Rubrospinal tract
Red nucleus (midbrain) to SC. Innervates UE flexors.
Tectospinal tract
Superior colliculus to upper SC.
To neck ms.
Symptoms associated with LMN lesions (5)
Flaccid paralysis Wasting/atrophy Hyporeflexia Hypotonia Fasciculations
Symptoms associated with UMN lesions (
Loss of distal extremity strength.
Babinski sign (inverted plantar reflex)
Hypertonia (spasticity, rigidity)
Hyperreflexia
Spasticity is indicative of:
Rigidity is indicative of:
Spasticity: UMN lesion
-rate dependent w/ loss of resistance at end of ROM.
Rigidity: basal ganglia disease
-rate independent, constant throughout ROM.
LMN damage result in clinical signs where?
IL to the lesion
UMN lesions above the medulla will have clinical signs where?
CL to the lesion
UMN lesions in the SC will have clinical signs where?
IL to the lesion
Decorticate posture is a result of a lesions where?
What’s the posture?
Lesion above red nucleus.
Elbows flexed and arms pronated w/ LE extension.
Decerebrate posture is a result of a lesion where?
What’s the posture?
Lesion below red nucleus, but above reticospinal and vestibulospinal nuclei.
UE pronated and in extension as well as the LE.
What are all of the deficits when there is a complete transection of the SC? (5)
All sensation lost 1-2 segments below lesion. Bladder/bowel control are lost. Spinal shock. UMN signs below lesion. LMN signs at the level of lesion.
What are the deficits when there is a hemisection of the SC?
Loss of pain and temperature from CL side of body (ALS).
Loss of discriminative touch and proprioception on IL side (PCMLS).
LMN signs at level of lesion.
UMN signs IL to lesion.
Brown-Sequard syndrome
Spyringomyelia affects:
First pain and temp (hits AWC first).
Cape and/or shawl pattern.
MAY have LMN signs at ventral horns.
MAY have UMN signs if lateral CST is affected.
Anterior cord syndrome
Damage/compression to anteriro part of SC.
Loss of IL motor from LCST and LMN.
Loss of CL ALS (pain and temp).
Central cord syndrome
AWC is hit –> BL loss of pain and temp.
If it hits anterior horns, there might be LMN problems.
Medial medullary syndrome
Arterial supply to medial medulla?
Hits pyramids, ML, and hypoglossal nucleus.
Pyramids: CL UMN sx.
ML: CL loss of PCML.
HN: IL protruding tongue.
Arterial supply: anterior spinal a.
Lateral medullary syndrome
Arterial supply?
Hits ALS, spinothalamic nucleus/tract, nucleus ambiguus.
ALS: CL loss of pain and temp.
ST N/T: IL loss of pain and temp to face.
Nucleus ambiguus: voice problems, dysphagia, CN IX, X problems.
Arterial supply: PICA
Central seven palsy
Lesion of corticobulbar tract w/ CN VII.
Upper facial muscles can function OK because fibers from both sides contirbute.
Muscles of lower face are controlled by CL hemisphere.
Lesion on left will have right-sided lower face paralysis.
Weber’s syndrome
Blood loss to parts of midbrain (CST, CBT, CN III).
CST: CL UMN sx.
CBT: CL low face droop.
CN III: down and out eye, dilated pupil.
Amyotrophic lateral sclerosis (ALS)
Destroys only somatic neurons.
Leads to UMN sx.
CN involvement leads to problems breathing, swallowing, speaking.
